Features

Trends in Polymers for Skin Care

April 30, 2009

More on recent patent activities that are of interest to the cosmetic chemist; specifically film-forming polymers, particles and polymer stabilization and various encapsulation techniques.

Trends in Polymers for Skin Care



More on recent patent activities that are of interest to the cosmetic chemist; specifically film-forming polymers, particles and polymer stabilization and various encapsulation techniques.



Part I
Robert Y. Lochhead
The Institute for Formulation Science and The School of Polymers & High Performance Materials
The University of Southern Mississippi



Last month, I surveyed recently published U.S. patents and applications and identified emerging trends in polymers, including their use as emulsion stabilizers, rheology modifiers, and protein block and graft copolymers. In Part II of this article, I review activity pertaining tofilm-forming polymers, particles and polymer stabilization, facial masks, pilosebaceous delivery capsules and soap encapsulation.

Film-forming Polymers



Treating the skin with microorganisms such as probiotics has been proposed to provide benefits. However, the inclusion of live microorganisms into conventional product forms poses problems because the probiotic organisms remain viable only in creams and lotions that contain no preservatives. One way that has been proposed to overcome this problem is to package the microorganisms in a water-soluble polymer film.1 The microorganisms are applied to the target substrate by merely placing the film in contact with wet skin. Suitable film-forming water-soluble polymers for this applicaton include polyvinyl alcohol, hydroxypropylcellulose and carrageenan. A suitable probiotic is Bifidobacterium longum.

Film-forming polymers can also be used to provide long-wearing, smudge-proof makeup. In this context, it has been taught that a combination of two film-forming polymers and a cross- linked polymer can yield an eye makeup with excellent wear properties and easy removability when desired.2 The first film-forming polymer has a glass transition temperature ranging from about -20°C to about 0°C.

Polymers play an increasingly important role in the formulation of skin care masks.
This type of polymer is exemplified by an acrylates/octylacrylate copolymer, an ethyl acrylate/methyl methacrylate copolymer or an ethyl acrylate/methyl methacryalate/methacrylic acid copolymer available under the tradenames Daitosol 5000SJ or Daitosol 5000AD from Kobo Products, or Covacryl A15, Covacryl E14 and Covacryl P12 from Sensient Cosmetic Technologies. The second film-forming polymer has a glass transition temperature at least 50°C higher than the first polymer and polymers of this second type are exemplified by a mixture of acrylates/ hydroxyesters acrylates copolymer and polyvinyl acetate available as Thorco Flex IV G and Thorco Flex-3 from Thomley Company.

The crosslinked polymer is exemplified by acryloyl dimethyltaurate/vinyl pyrrolidone crosspolymer or acryloyl di- methyltaurate/beheneth-25 methacrylate crosspolymer available under the tradenames Aristoflex AVC, AVL or HMB from Clariant Corporation, or acryates/C10-C30 alkyl acrylate crosspolymer available under the tradenames Pemulen TR-1 and TR-2 from Lubrizol Advanced Materials.

Particles & Polymer Stabilization



“Dry water” compositions are dry-feeling, free-flowing powders that contain imbibed water that is released by shear and pressure when rubbed on the skin. Such compositions have the appearance of a powder but the aesthetics, the fresh feel and the cooling characteristics of a lotion. This is achieved by covering the aqueous component with hydrophobic particles. Excellent feel characteristics and product stability are taught to result from the combination of specific hydrophobic particles, plate-like polymer particles and an aqueous component that releases water on rubbing.3 Suitable hydrophobic particles are hydrophobically-modified fumed silica. Polystyrene of acrylate or methacrylate polymers are plated out as thin films which are then pulverized to yield the plate-like particles. The aqueous component consists of gels of agar, gelatin, carageenan, gellan gum, magnesium sodium silicate or sclerotium gum.

Monodisperse polymer latex particles can be laid in precise “colloid crystal” layers that diffract light to produce iridescence much like that observed from peacock feathers. This principle has been applied to makeup by placing sterically-stabilized (or “hairy”) monodisperse particles to decorate the skin.4,5 The particles are exemplified by polystyrene latex stabilized by poly(N-isopropylacrylamide) grafted to the polystyrene particle surface. This choice of stabilizing polymer is interesting because poly(N-isopropylacrylamide) is soluble in water at room temperature but it phase separates when the aqueous solution is warmed to human physiological temperature. In this application, the monodisperse “hairy” particles are applied to a base coat to assure uniform distribution of the particle on the substrate surface. After the particle layer has dried (in about 30 seconds) a topcoat is added to keep the particles in place during the period of wear and/or to alter the optical characteristics of the coating. Film formation of the base coat can be assisted by including coalescing agents and volatile solvents. The film-forming polymers for the base coat can be, for example, Ultrasol 2075 from Ganz Chemical, Daitosol 5000AD from Daito Kasei; Avalure UR 450 from Lubrizol Advanced Materials, Dynamx from National Starch, Syntran 5760 from Interpolymer, Acusol OP 301 from Rohm & Haas, or Neocryl A 1090 from Avecia.

Facial Masks



Microcapsules can be incorporated into facial masks to impart skin-lightening effects in addition to other skin benefits.6 The microcapsules in this case are made of polyamines such as polyoxymethylene melamine urea (PMU) and they contain a liquid impregnate having a viscosity of less than 10,000cps.

The invention is exemplified by delivering the liquid impregnate for Neutrogena Fine Fairness Mask with Vitamin C, into aminoplast microcapsules from Reed Pacific. The particles were incorporated into a mask that conferred an “immediate” increase in skin whitening when applied to the face.

Skin lightening is an important product category in the Asia-Pacific region. This recent patent, assigned to Johnson & Johnson, was granted over prior art from Charle et. al.,7 Norbury et. al.,8 Slavtcheff et. al.9 and Lang et. al.10 Charle et. al. claim asheet or web containing a uniform distribution of pressure-rupturable microcapsules that contain liquid or semi-solid cosmetic treatments. The uniform distribution is produced by matching the density of the liquid suspension to the solid support of the microcapsule. The composition within the microcapsule may be a sun oil, a moisturizing facial cream, a foundation or a gradual hair dye composition. The microcapsules may be made from any of a large variety of polymers including polyamides, epoxy resins, silicones, polyethylene, urea-formaldehyde resin, and gum Arabic. Thus, acrylic acid microcapsules that contained cream were incorporated into cellulose isobutyrate, dried and placed in absorbent paper napkins to produce makeup-removing towels. Norbury et. al. describe a flat support layer to which frangible liquid containing microcapsules are adhered. Slavtcheff et. al. claim an adhesive cosmetic strip that contains a component that heats up when exposed to water. The strip also contains a liquid crystal thermometer device that produces a color change to signal the temperature rise. In this respect, they advocate skin treatment compositions containing water-dispersed resin microcapsules impregnated with cholesteryl ester carbonate. However, Charle, Norbury and Slavtchef do not recommend products that contain a liquid impregnate of less than 10,000 cps in the microcapsules for treating the skin, and Slavtcheff’s skin products are “dry to the touch.”

Lang et. al describe nonwovens that have binder compositions comprising ion-sensitive, water-dispersible polymers. The polymers function as binders in the presence of ion-containing body fluids, but they disperse in water—even hard water—and this results in a flushable nonwoven wipe. Lang suggests microcapsules as a preferred delivery method for skin care agents in wet wipes, but not for products intended to be applied to the skin for a period of time to achieve skin-lightening benefits. A nasal strip incorporating microcapsules was described by Anderson et. al.11 The strip contained fragrances or medication and the microcapsules prolonged the effectiveness of this imbibed liquid but Anderson’s invention is not directed toward applying beneficial liquids to skin from microcapsules.

Pilosebaceous Delivery Capsules



The pilosebaceous unit is responsible for the formation of sebum on the surface of skin. This site can also be the point of infection and inflammation such as acne. However, the pilosebaceous unit can also be a “port of entry” for deep skin tissue treatments such as anti-wrinkle treatments. There is a drawback insofar as the continuous outward flow of sebum opposes the desired penetration of treatment agents via the pilosebaceous ducts but this has not deterred attempts to deliver materials via this route:
• 3 to 10 micron diameter microspheres have been proposed for active transport into the pilosebaceous duct.12The microspheres are either cross- linked polymers or solid microspheres that are loaded by partial solubilization of the active material into the microspheres;
• Microsphere or Liposomes have been proposed as carriers of active compounds via the hair follicle in which they swell to enhance passage of the active agent into the follicle;13 and
• Microparticles, prepared by copolymerization of styrene, vinyl stearate and dimethylbenzene or methylmethacrylate and ethylene glycol dimethacrylate in the presence of a porogen, can be used for controlled release into the pilosebaceous unit. The porogen in this case is often the active agent.14

Soap Encapsulation



Soap in bar form has been available for almost as long as the practice of washing for personal cleansing. But there are two drawbacks to the soap bar form:
• It is not very transportable especially in its wet form and
• In public places a single bar is shared by all users; this can be unsanitary and repulsive to some.

Powder soaps were introduced to overcome the issue of soap-sharing in public but powdered soap is messy and it leaves unsightly deposits in washbasins. Moreover, powdered soap is not convenient for the traveler. Liquid and gel soaps can be dispensed to individual users but they require dispensers, which limits portability.

The need for a portable soap that is available in individual doses has been addressed by the invention of an encapsulated surfactant form that also contains a hydrocarbon propellant that confers “instant” foaming upon use.15Encapsulated soap is not new, but encapsulated soap that contains a foam-triggering propellant is sufficiently new for the U.S. Patent Office to grant a patent. The encapsulating polymeric materials that are disclosed include cellulose derivatives such as cellulose, cellulose ester, cellulose ether, cellulose nitrate, cellulose triacetate, cellulose acetate phthate (CAP), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC), and hydroxypropyl methylcellulose phthalate (HPMCP); acrylate polymers such as polyacrylate, polymethylacrylate, poly(acrylatemeth- ylacrylate), poly(methacrylate-methylmethacrylate), poly(ethylacrylate- methylmethacrylate), poly (ethylacrylate-methylmethacrylatetrimethylammonioethylmethacrylate chloride), and poly(ethylacrylate-methylmethacrylatetrimethylammonioethylmethacrylate chloride); vinyl polymers such as polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, polystyrene and polyacrylonitrile; polyolefins such as polyethylene, polypropylene, and polybutylene; proteins such as albumen; and process whey protein; and polysaccharides such as guar hydroxypropyl trimonium chloride.

Inside the encapsulants, there is a barrier layer that is a stable coating in direct contact with the cleansing liquid. It is desirable that the capsule should disintegrate from the inside by dilution with water, change of pH, or mechanical forces such as abrasion or agitation. Suitable polymers are water-soluble compounds that display an upper critical solution temperature in the desired temperature range—the range can be adjusted by the addition of salt to the solution. Suitable polymers for the barrier layer are polyvinyl alcohol; polyvinyl pyrrolidone and its various copolymers with styrene and vinyl acetate; and polyacrylamide and its derivatives. The barrier layer can also be made up of modified polysaccharides and proteins such as carrageenan, guar gum, pectin, xanthan gum, partially hydrolyzed cellulose acetate, hydroxy ethyl, hydroxypropyl and hydroxybutyl cellulose, methyl cellulose and gelatin. The novelty of this newly-patented invention lies in the presence of a propellant to initiate foaming.

Prior inventions have included:
• Cleansing agents in the form of bodies made from multiple shells which dissolve in washing. The shells are made of detergent or multiple detergents, including detergent jelly.16
• “Surfactants,” selected from sodium dioctylsulfosuccinate, sodium carboxy- methylcellulose, sorbitan sesquio- leate, silicones, and/or PVM/MA encapsulated in a shell of wax, sugars, natural gums, synthetic polymers, or gelatin. For example, a liquid fill of 69.98% isopropanol, 30% water and 0.02% carbomer is encapsulated in a microcrystalline wax shell.17 The content of the capsule can be released by heat, pressure or dissolution, depending upon the desired trigger.
• Liquid surfactant formulations in a receptacle composed of water-soluble polymer, in which the receptacle dissolves during use. In order to prevent dissolution of the water-soluble polymer during the capsule’s shelf-life, it may be necessary to coat the inside of the receptacle with polymers such as polyvinylidene chloride or PTFE.18

In conclusion, it is clearthat innovation in personal care polymers continues to proceed at an impressive pace.

References


1. Cassin; Guillaume; Simonnet; Jean-Thierry; Cosmetic water-soluble film, US Patent App. 20090022700, Jan. 22, 2009; Assigned to L’Oréal.
2. Marotta, Paul H.; Flanagan, Katie A.; Tabakman, Tatyana R.; Castro, John R.; Martin, Elizabeth M.; Cosmetic Composition Containing a Polymer Blend, US Patent App. 20090035335, Feb. 5, 2009.
3. Igarashi, Keiji; Hydrous powdery cosmetic preparation, US Patent App. 20090060959; March 5, 2009; assigned to Kose Corporation.
4. Dumousseaux, Christophe; Composi- tions for Making Up Keratinous Materials; US Patent App. 20090041696, Feb. 12, 2009 assigned to L’Oréal.
5. Dumousseaux, Christophe; Kawamoto, Makoto; Compositions for Making Up Keratinous Materials; US Patent App. 20090041695, Feb. 12, 2009 assigned to L’Oréal.
6. Lambino, Danilo; Loh, Christine; Estanislao, Roderico; Khaiat, Alain; Product for treating the skin comprising a polyamine microcapsule wall and a skin lightening agent; US Patent 7,452,547, Nov. 18, 2008; assigned to Johnson&Johnson Consumer Co., Inc.
7. Charle, Roger; Zviak, Charles; Kalopis- sis, Gregoir, Towels, tissues and the like comprising encapsulated cosmetics, GB Patent 1,304,375, Jan. 24, 1973, assigned to L’Oréal.
8. Norbury; R. James, Pendergrass, Jr.; Daniel B.; Liquid transfer device, US Patent 4,878,775; Nov. 7, 1989. assigned to Minnesota Mining and Manufacturing Co.
9. Slavtcheff, Craig Stephen; Znaiden, Alexander Paul; Indursky, Michael; Crotty, Brian Andrew; Cosmetic strips with liquid crystal temperature dependent color change; US Patent 6,270,783, Aug. 7, 2001; assigned to Unilever Home & Personal Care USA, division of Conopco, Inc.
10. Lang, Frederick J.;Branham, Kelly D.; Chang, Yihua;, Chen, Franklin M.; Johnson; Eric D.; Lindsay, Jeffrey D.;, Mumick, Pavneet S.; Pomplun,William S.; Schick, Kim G.; Schultz, Walter T.; Soerens, Dave A.; Sun, Tong; Wang, Kenneth Y.; Ion-sensitive, water-dispersible polymers, a method of making same and items using same, US Patent 6,429,261; Aug. 6, 2002; assigned to Kimberly-Clark Worldwide, Inc.
11. Anderson, Milton W.; Hashizume, Nobuya; Cronk, Peter J.; Cronk, Kristen; Microencapsulated fragrances and methods of coating microcapsules, US Patent 6,550,474, April 22, 2003; assigned to CNS, Inc.
12. Schaefer, Hans; Watts, Francine; Mahieu, Claude; Composition cosmetique ou pharmaceutique contenant des microspheresde polymers ou de corps gras chargees d’au moins un produit actif, EU Patent app. 0375520, June 27, 1990, assigned to Center International de Recherches Dermato- logiques C.I.R.D.
13. Sumian, Chryslain; Enhancing compound penetration into and through hair follicles, WO 02/07674, Jan. 31, 2002; applicant is Ceramoptec Industries, Inc.
14. Won, Richard; Method for delivering an active ingredient by controlled time releaseutilizing a novel delivery vehicle which can be prepared by a process utilizing the active ingredient as the porogen; US Patent 4,690,825, Sept. 1, 1987, Assigned to Advanced Polymer Systems.
15. Reddy, Kiran K.; Yang, Ning; Skerrett, John Richard; Provenzano, Guy William; Welchel, Debra N.; Encapsulated liquid cleanser, US Patent 7,485,609, Feb. 3, 2009, assigned to Kimberly-Clark Worldwide, Inc.
16. Raion Yushi Kabushiki, Cleansing agent having shell structure, GB Patent 1,307,387, Feb. 21, 1973
17. Bolles, Theodore F.; Capsules and process for forming capsules; US Patent 3,779,942, Dec. 18, 1973; assigned to Minnesota Mining and Manufacturing Company
18. Duffield, Paul John; Hammond, Geoffrey Robert; Edwards, David Brian; McCarthy, William John; Beckett, Arnold Heyworth; Jackman, Anthony Douglas; Injection-molded water soluble container, US Patent App. 20030108705, June 12, 2003; assigned to Reckitt Benckiser

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